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From: <bp@www.zefox.net>
Newsgroups: sci.electronics.design
Subject: Re: OT: Repeatably lobbing "projectiles"
Date: Fri, 22 Nov 2024 18:30:05 -0000 (UTC)
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Don Y <blockedofcourse@foo.invalid> wrote:
> 
> The point is finding the right combination of mechanism
> and projectile to get repeatability from the system.

Yes, repeatability is the first requirement for accuracy.

> Most "guns" just want to achieve a "maximum" (range,
> load, etc.)

Not sure I understand what you're getting at here. On
the face of it that statement seems mistaken.

Perhaps the most clever feature of the Giradoni mechanism
is pitting the momentum of the hammer _against_ the air pressure
bearing on the release valve. As the pressure goes down, the
valve opens farther, at least partially compensating for the
lower pressure. 

Since you will have control of the exact pressure that particular
compensation isn't needed. Still, if the valve opens differently
on timescales comparable to the departure time of the projectile
repeatability will suffer and with it accuracy. Opening the valve
poppet before the projectile moves is one way to help repeatability.
For the velocities you envision that shouldn't be difficult. 

A pneumatic potato cannon seems like a good starting point.

bob prohaska